Whether privilege can be only be waived by someone who is aware of their rights

http://www.bailii.org/ew/cases/EWHC/Ch/2015/1003.html

This case involved alleged waiver of legal advice privilege by executors. Of general interest is the argument raised by one of the executors that his reference to advice given to him by his solicitors did not amount to a waiver because he had not been aware of his rights at the time. The executor referred to the general principle that a right cannot be waived unless a person is aware of his right of election as well as the facts giving rise to it (see eg Peyman v Lanjani [1985]).

However, Newey J confirmed that that principle does not apply to waiver of privilege. In so doing he cited Thanki, "The Law of Privilege": "the basic position in England is that once the substance of privileged material is divulged to one's opponent, even by accident and even where there is no implication of an intention to waive, privilege is prima facie lost" and that waiver in this context differs from its meaning elsewhere in the law. The judge also rejected an argument that privilege can be waived by accident only at trial or as a result of disclosure by list and inspection: "To my mind, however, privilege can be waived by inadvertence at any point".

However, the judge did note that it may be easier to remedy a mistake made in advance of trial (eg by applying for an injunction or relying on CPR r31.20 (which provides that where a party inadvertently allows a privileged document to be inspected, the other side can use it only with the permission of the court).